The present invention relates generally to the introduction of various fluids into a patient, and more particularly to the alteration of the temperature of the fluids prior to their introduction so that the fluids are within a desired temperature range when introduced. In one particular aspect, the fluids are pressurized to facilitate their introduction into the patient at a desired rate and volume, thereby allowing the fluids to be introduced without relying on the assistance of gravity.
Various medical procedures rely on the introduction of different fluids into the body, often directly into the blood stream. In many cases, it is desirable to have such fluids introduced while the temperature of the fluids are within a desired range. For example, as described in copending U.S. application Ser. No. 08/769,931, filed Dec. 19, 1996 (Attorney Docket No. 19766-707), the complete disclosure of which is herein incorporated by reference, heated or cooled fluids may be introduced into a patient suffering from hypothermia or hyperthermia, or for neuro protection. Copending U.S. application Ser. No. 08/769,931, filed Dec. 19, 1996, describes various catheter embodiments which heat or cool a fluid while the fluid is within the patient. In this manner, a fluid may be heated to a desired temperature to raise the patient""s core body temperature and thereby reduce or eliminate the symptoms of hypothermia. Alternatively, such catheter embodiments may be employed to cool the fluid while within the patient to lower the patient""s core body temperature. Cooling of the fluid while within the patient may also be employed by such catheter embodiments to cool a specific region of tissue prior to performing a surgical procedure.
In many cases the treatment of a patient requires urgent medical attention and may therefore limit the types of equipment that may be used for treatment. For instance, in cases where the introduction of fluids into the patient is a prescribed treatment, the fluids must be introduced into the patient as quickly as possible. In such cases, it would therefore be desirable to provide a portable system that could be used in the field or in an ambulance to rapidly infuse various fluids which are within a desired temperature range into the patient.
Many existing fluid introduction systems rely on a gravity feed system where the fluid is held within a is compressible structure, such as an IV bag. However, such gravity feed systems are often inconvenient in cases where urgent treatment is required, such as in the field or in tight spaces where elevation of the IV bag is impossible, e.g. in an ambulance. For example, without proper elevation, it is difficult to regulate the rate and volume of fluid introduction.
Another drawback of such gravity feed systems is the difficulty in regulating the temperature of the fluid within the IV bag. Hence, with such systems it is difficult to ensure the fluid is at the proper temperature when introduced into the patient.
Hence, for these and other reasons, it would be desirable to provide systems and methods which would place a fluid within a desired temperature range prior to its introduction into a patient. Such systems and methods should also be conducive to urgent care settings which require mobility, manipulation in tight spaces and rapid preparation. Such systems and methods should also be able to precisely control the rate and volume of fluid introduction into the patient. Further, in some cases it would be desirable if the systems and methods were able to place the fluids within the desired temperature range while the fluids are within conventional containers, such as IV bags.
The invention provides systems and methods for infusing fluids into a patient. According to the invention, the fluids may be infused into the patient in a variety of ways, including intraveneously, intra-arterially, peritoneally (intra-abdominally), and the like. In one exemplary embodiment, a system is provided comprising a volume of fluid, and a temperature altering device in close proximity to the volume of the fluid to heat or cool the fluid to a desired temperature. A positive pressure device is further provided to place the volume of fluid under positive pressure while at the desired temperature. A transfer member is provided to transfer at least some of the fluid into the patient while the fluid is at the desired temperature.
In one aspect of the system, the temperature altering device comprises a heater to heat the fluid to a temperature which is within the range from about 36xc2x0 C. to about 42xc2x0 C. Alternatively, the temperature altering device may comprise a cooler to cool the fluid to a temperature within the range from about 0xc2x0 C. to about 35xc2x0 C.
In another aspect, the system further includes a reservoir, such as a compressible bag, for holding the volume of fluid. The transfer member is operably connected to the reservoir, and a flow regulator is provided to regulate the flow of fluid from the reservoir and into the transfer member. The flow regulator preferably comprises a controller which regulate the application of pressure from the positive pressure device. In one particular aspect, the flow regulator will preferably regulate both the rate and volume of the fluid removed from the reservoir.
In still another aspect, the transfer member comprises a length of tubing to which an end dwelling device, such as a needle, catheter, sheath, or the like may be attached to infuse the fluid into the patient. In still another aspect, a controller is provided to monitor the temperature of the volume of fluid and to control actuation of the temperature altering device.
In one particular aspect, the temperature altering device comprises a housing having inner walls which define a chamber. The fluid is held within the chamber, and the housing includes temperature altering elements to heat or cool the inner walls of the housing to alter the temperature of the fluid. A variety of temperature altering elements may be provided to either heat or cool the inner walls such as electrical resistors, chemicals, frozen liquids, heated liquids, heated gases, radio frequency electrodes, thermoelectric crystals, and the like.
In another particular aspect, the positive pressure device comprises a plate and a compressor for moving the plate against the volume of fluid to compress the fluid. Exemplary compressors for moving the plate include springs, hydraulics, is solenoids, and the like. Alternatively, the positive pressure device may comprise a bladder and a pressure source to expand the bladder against the volume of fluid.
The system may be employed to introduce a wide variety of fluids into the patient. Such fluids may include, for example, blood, saline solutions, drugs, solutes and the like.
The invention further provides an exemplary method for infusing a fluid into a patient. According to the method, a volume of fluid is provided and is at an initial temperature. The temperature of the fluid is altered until the fluid is at a desired temperature. While at the desired temperature, the fluid is pressurized to introduce the fluid into the patient at the desired temperature.
The pressure applied to the fluid will preferably be regulated so that the fluid is introduced into the patient at a predetermined rate and volume. In one exemplary aspect, the pressurized liquid is flowed through a tube which is intravenously inserted into the patient to introduce the fluid directly into the patient""s blood stream.
In a further aspect, the fluid is heated to the desired temperature which is within the range from about 36xc2x0 C. to about 42xc2x0 C. Alternatively, the fluid may be cooled to the desired temperature which is in the range from about 0xc2x0 C. to about 35xc2x0 C. In one particularly preferable aspect, the temperature is altered by placing the volume of fluid into a housing having inner walls which define a chamber. The inner walls are then heated or cooled to alter the temperature of the fluid within the chamber.
In another particularly preferable aspect, the fluid is pressurized by compressing the volume of liquid with a plate. Alternatively, the fluid may be pressurized by inflating a bladder which presses against the volume of fluid. The volume of fluid may be selected from a wide variety of fluids including blood, saline solutions, drugs, solutes and the like. In one aspect, the volume of fluid will preferably be held within a compressible bag, with the temperature of the fluid being altered while within the bag.